Simplify the following expression: $k = \dfrac{2st - 2rt}{2t^2 + 3rt} - \dfrac{6t^2}{2t^2 + 3rt}$ You can assume $r,s,t \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{2st - 2rt - (6t^2)}{2t^2 + 3rt}$ $k = \dfrac{2st - 2rt - 6t^2}{2t^2 + 3rt}$ The numerator and denominator have a common factor of $t$, so we can simplify $k = \dfrac{2s - 2r - 6t}{2t + 3r}$